Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years in the past. Tyson further explains how modern astronomy has used such analyzes via deep time to identify the Big Bang event and the age of the universe. Tyson proceeds to describe how the work of Isaac Newton, William Herschel, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson describes the concept of dark stars as postulated by John Michell which are not visible but detectable by tracking other stars trapped within their gravity wells, an idea Herschel used to discover binary stars. Tyson then describes the nature of black holes, their enormous gravitational forces that can even capture light, and their discovery via X-ray sources such as Cygnus X-1. Tyson uses the Ship of Imagination to provide a postulate of the warping of spacetime and time dilation as one enters the event horizon of the black hole, and the possibility that these may lead to other points within our universe or others, or even time travel. Tyson ends on noting that Herschel's son, John would be inspired by his father to continue to document the known stars as well as contributions towards photography that play on the same nature of deep time used by astronomers.

We will nvestigate the first skeleton that really looks like us –Turkana Boy– an astonishingly complete specimen of Homo erectus found by the famous Leakey team in Kenya. These early humans are thought to have developed key innovations that helped them thrive, including hunting large prey, the use of fire, and extensive social bonds. The program examines an intriguing theory that long-distance running –our ability to jog– was crucial for the survival of these early hominids. Not only did running help them escape from vicious predators roaming the grasslands, but it also gave them a unique hunting strategy: chasing down prey animals such as deer and antelope to the point of exhaustion. Birth of Humanity also probes how, why, and when humans' uniquely long period of childhood and parenting began.

xamines the fate of the Neanderthals, our European cousins who died out as modern humans spread from Africa into Europe during the Ice Age. Did modern humans interbreed with Neanderthals or exterminate them? The program explores crucial evidence from the recent decoding of the Neanderthal genome. How did modern humans take over the world? New evidence suggests that they left Africa and colonized the rest of the globe far earlier, and for different reasons, than previously thought. As for Homo sapiens, we have planet Earth to ourselves today, but that's a very recent and unusual situation. For millions of years, many kinds of hominids co-existed. At one time Homo sapiens shared the planet with Neanderthals, Homo erectus, and the mysterious "Hobbits"–three-foot-high humans who thrived on the Indonesian island of Flores until as recently as 12,000 years ago. "Last Human Standing" examines why "we" survived while those other ancestral cousins died out. And it explores the provocative question: In what ways are we still evolving today?

Carl Sagan teaches students in a classroom in his childhood home in Brooklyn, New York, which leads into a history of the different mythologies about stars and the gradual revelation of their true nature. In ancient Greece, some philosophers (Aristarchus of Samos, Thales of Miletus, Anaximander, Theodorus of Samos, Empedocles, Democritus) freely pursue scientific knowledge, while others (Plato, Aristotle, and the Pythagoreans) advocate slavery and epistemic secrecy.

Beginning with the origins of the universe in the Big Bang, Sagan describes the formation of different types of galaxies and anomalies such as galactic collisions and quasars. The episodes moves further into ideas about the structure of the Universe, such as different dimensions (in the imaginary Flatland and four-dimensional hypercubes), an infinite vs. a finite universe, and the idea of an oscillating Universe (similar to that in Hindu cosmology). The search into other ideas such as dark matter and the multiverse is shown, using tools such as the Very Large Array in New Mexico. Cosmos Update shows new information about the odd, irregular surfaces of galaxies and the Milky Way perhaps being a barred spiral galaxy

The idea of intelligence is explored in the concepts of computers (using bits as their basic units of information), whales (in their songs and their disruptions by human activities), DNA, the human brain (the evolution of the brain stem, frontal lobes, neurons, cerebral hemispheres, and corpus callosum under the Triune Brain Model), and man-made structures for collective intelligence (cities, libraries, books, computers, and satellites). The episode ends with speculation on alien intelligence and the information conveyed on the Voyager Golden Record.